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Darwin Correspondence Project

From W. T. Thiselton-Dyer   25 June 1874

10 Gloucester Road, Kew

June 25. 1874

Dear Mr Darwin

Several days ago I began answering your letter which I had indeed already delayed doing too long.1 I was anxious, however, to get you as much information as I could and some of your inquiries I must still leave in suspense.

1. I could not positively affirm that all the species of Pinguicula secrete because one could not do this without having seen them all growing.2 But I have looked at all the species of which there are dried specimens in the Kew Herbarium and they have all much the same habit with one or two exceptions. There is an american species P. filifolia, Wr. with long slender leaves. A Ms. note with the specimens speaks, if I remember rightly, of the leaves being “icy” like the other species. I imagine therefore that even that ‘secretes’ though I have no notion how the leaves are disposed when it grows.3 In the character of the genus given in DeCandolle’s Prodromus the leaves are described as “rosulatis, integerrimis, margine plerumque involutis.”4 As far as one can judge from dried specimens which in the case of succulent plants are never very satisfactory, the curving up of the margin for the purpose of retaining the secretion seems to be general throughout the genus.

Have you noticed the curious trick the plants have of rolling their leaves downwards when pulled up— This is a considerable practical difficulty in the way of getting good herbarium specimens.


2. I asked Dr Hooker about some botanist who could make observations for you and he suggested Mr Ralfs of Penzance at which place the Irish P. grandiflora has been naturalized in a bog.5 In the Student’s Flora it is however I see reduced to a variety of P. vulgaris and you would like a wider specific range.6 I think I could get plants sent you from Ireland if you would care to have

CD annotations

1.1 Several … suspense. 1.3] crossed blue crayon
2.5 filifolia,] underl blue crayon
2.9 rosulatisinvolutis.”] double scored pencil
3.1 Have … specimens. 3.3] scored blue crayon
4.1 2.... to have 4.5] crossed pencil
Top of letter: ‘It is all confusion about exalbuminous seeds7 | p. 1. d. | generic characters of genus’ pencil: ‘Movement | Generic Characters’ blue crayon


Pinguicula filifolia, described by Charles Wright, is endemic to Cuba.
Thiselton-Dyer refers to A. P. de Candolle and Candolle 1824–73. Rosulatis, integerrimis, margine plerumque involutis: arranged in a rosette, smooth, edges generally curled (Latin).
See letter to W. T. Thiselton-Dyer, 9 June 1874, for CD’s request for names of possible observers of Pinguicula (butterwort); the botanist John Ralfs was known to Joseph Dalton Hooker (see Correspondence vol. 7, letter from J. D. Hooker, 12 November 1858).
See letter to W. T. Thiselton-Dyer, 9 June 1874. Exalbuminous: having no albumen.


Candolle, Augustin Pyramus de and Candolle, Alphonse de. 1824–73. Prodromus systematis naturalis regni vegetabilis, sive enumeratio contracta ordinum generum specierumque plantarum huc usque cognitarum, juxta methodi naturalis normas digesta. 19 vols. Paris: Treuttel & Würtz [and others].

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Hooker, Joseph Dalton. 1870. The student’s flora of the British Islands. London: Macmillan.


Reports on his examination of the dried specimens of Pinguicula at Kew to answer CD’s query whether all species secrete.

Letter details

Letter no.
William Turner Thiselton-Dyer
Charles Robert Darwin
Sent from
Source of text
DAR 58.1: 64–6
Physical description
inc †

Please cite as

Darwin Correspondence Project, “Letter no. 9513,” accessed on 22 April 2024,

Also published in The Correspondence of Charles Darwin, vol. 22